The overall direction of our program is to develop and apply radioactive tracer technology to the study of chemical processes going on at different sites within the body i.e. to facilitate the study of the in vivo biochemistry of the living human body. The techniques that we have developed in the past and propose to continue to develop in the future help elucidate "biochemical anatomy", the topography of physicochemical processes, extending the cellular basis of disease to the molecular level. Our program requires multidisciplinary participation of physicians, physicists, chemists, engineers, and computer experts; and is multidepartmental, involving departments in both the Schools of Medicine and Hygiene and Public Health of the Johns Hopkins Medical Institutions. The program provides a focus for investigators in a continuing program oriented toward obtaining new knowledge about the dynamic state of body constituents by the application of a variety of in vivo biochemistry, identifying hyper- or hypoactive states associated with abnormal body functions.